Conventional hubs, such as marine propeller hubs, are axially positioned on a tapered end of a shaft. The propeller and hub assembly is attached to the shaft for following movement through the use of a key secured in a keyway between the shaft and hub. A variety of key shapes and combinations with other elements have been used in the past to prevent movement of the key in the keyway during use. Such movement can occur when the speed of rotation of the hub is altered or the direction of rotation of the hub is changed. Thus, the key tends to slide longitudinally in the keyway in one direction or the other dependent primarily on the direction of rotation of the shaft. When the key is permitted to slide and move relative to the surfaces of the keyway in the shaft, the hub and the surface of the key may become misaligned, setting up a situation in which, under the stress of use, can cause fractures and breaking of the shaft end, lost propellers, and the like. In an effort to correct these problems tapered keys have been used for achieving a wedging action to take up any slack motion which may exist between the parts, as set forth in U.S. Pat. No. 3,877,828. Others, as taught in U.S. Pat. No. 3,862,808, have provided lateral positioning lugs on one end of the key and placement of the key in an axial keyway with corresponding lateral shoulders so that the key may not move axially in a forward direction. Still others have held the key rigidly in the keyway through the use of screws, as in U.S. Pat. No. 3,180,164.
In addition, with the mating tapered surfaces which are used in joining marine propellers and propeller shafts, a keyway which closely borders all sides of the key requires that the mating surfaces be precisely machined, with exacting tolerances, so that the mating tapered surfaces are joined at a predetermined position of the shaft. Generally, when a keyway has no provision for a stop at either end of the propeller, i.e., has a line of sight passageway therethrough, the key is apt to slide in the keyway during both installation and operation of the propeller.
There are teachings in the prior art which enclose the keyway on the propeller hub, thereby restricting movement of the key; however, placement of the hub on the propeller shaft becomes difficult, if not impossible, as an assemblyman must first expand the hub, as by heating, and then squeeze the hub over the key into place on the shaft. With the rigid materials generally in the use in the marine field, such expansion without permanent deformation is not possible without utilizing exotic and expensive materials.
Such a difficult procedure is demonstrated in the turbine field by U.S. Pat. No. 3,877,827, which attempted to solve the above described problem by providing a projection which extends outwardly for insertion into a mating circumferential groove in a surrounding collar or disc. The projection must be small enough to permit the disc to slide over it and onto the shaft when heated for expansion purposes.